Electric fuse

ABSTRACT

An electric fuse, especially for electric lighters in motor vehicles, comprising electrically conductive fusible means for releasing at a given temperature an electrically conductive metal plate to open the electric circuit and interrupt the supply of current.

United States Patent Pramaggiore [541 ELECTRIC FUSE [72] Inventor: LuigiAosta l4, Aosta, Italy [22] Filed: Sept. 9, 1970 [21] Appl.No.: 70,853

30 Eoreign Application Priority Data Apr. 1 1, 1970 Italy ..68234 A17052 1 11.5. C1. ..337/404, 219/263 511 1111.01. H0lh 37/76 [58] FieldofSearch ..337/40l,404,405,407,416; 219/262-264 [56] References CitedUNITED STATES PATENTS 3,323,458 6/1967 Hartmann, Jr ..337/40lPramaggiore, Corsa Battaglione Feb. 8, 1972 FOREIGN PATENTS ORAPPLICATIONS 668,041 8/1963 Canada 1,577,002 6/1969 France PrimaryExaminer-J. V. Truhe Assistant Examiner-J. G. Smith Attomey-Emest A.Greenside [57] ABSTRACT An electric fuse, especially for electriclighters in motor vehicles, comprising electrically conductive fusiblemeans for releasing at a given temperature an electrically conductivemetal plate to open the electric circuit and interrupt the supply ofcurrent.

V S CIaims, 3 Figures ELECTRIC FUSE This invention relates to anelectric fuse, especially for electric lighters in motor vehicles.

It is known that there is a considerable risk of motor vehicles catchingfire due to defects in the operation of the electric lighter installedtherein.

it is an object of the present invention to eliminate this risk byproviding an electric fuse which can be attached to the electric lighterand comprises electrically conductive fusible means for releasing at agiven temperature an electrically conductive metal plate to open theelectric circuit and interrupt the supply of current. In this way thesupply of current can be automatically stopped when the resistor of theelectric lighter remains continuously energized because of somemisfunction of the electric lighter.

The essential or operative part of the fuse is mode of metal or an alloywhich will melt at a low temperature, for example, a lead alloy, so thatwhen the electric lighter is energized by the rated electric current ofthe circuit in which it is inserted, the operative part will not benoticeably heated whereas it will be overheated until it melts when theelectric resistor is energized longer than a predetermined periodwhereby the circuit protected by the fuse is interrupted.

The fuse according to the invention may be applied, for example, to anelectric lighter for motor vehicles of the type described in applicantsItalian Pat. No. 570,238 of Apr. 19, 1957. In this case the fuse ismounted on the shaft projecting from the rear of the lighter whereconventionally the terminal plate for connection to the electric feedcable is secured.

More particularly the fuse according to the invention comprises asupporting receptacle of insulating material accommodating a fusibleelement in the form of a washer while another metal washer and finally anut hold the pack thus formed together on the rear shaft or pin of thelighter in the manner of a riveting.

Between the fusible element and the receptacle of insulating materialadvantageously a small blade projecting from a tombac leaf spring may besecured to establish electric connection between the current supplyterminal plate and the resistor of the lighter so that when the thermalelement melts due to heating produced by the heat coming from thelighter body, the leaf spring will be released and come out of the packof the fuse to interrupt the electric circuit. Normally when theelectric circuit is closed the leaf spring will be wound around the.

curved periphery of the receptacle with the free end of the leaf springinserted between the metal washer and the fusible washer and adheringfor a small distance around the periphery of the shaft of the centraleyelet in which the rear shaft of the lighter is accommodated. When thefusible washer of lead alloy has melted the leaf spring straightens dueto its elasticity and opens or interrupts the electric circuit.

Thus the fuse according to the invention ensures the interruption of theelectric current supply when there is a short circuit or when thetemperature in the lighter rises beyond a predetermined limit. Apartfrom electric lighters, the fuse according to the invention may also besupplied to many other electric devices.

Thus this fuse permits the regular passage of current as long as thedevice on which it is installed operates in the normal regular way, butit interrupts the supply of current in the case of a short circuit ordefect of operation of the device to be protected, for example, asmentioned above, when the temperature rises above a certain value.

A preferred embodiment of the invention will now be described by way ofexample and with reference to the accompanying drawing, in which:

FIG. 1 is a transverse section of a fuse according to the invention,shown on an enlarged scale;

FIG. 2 is a front view of the fuse in the closed or inoperative position(with the circuit closed), and

FIG. 3 is a similar view showing the fuse in the open position when thedevice is detached (with the circuit open).

The fuse or device according to the invention essentially consists of asupporting receptacle 1 preferably made of fiber I glass and havingincorporated therein and partly extending therefrom a brass terminal 4for connection to thelelectric feed cable (not shown). The portion ofthe terminal4 which is embedded in the receptacle 1 has a laterallyprojecting pointed lug 8 to which a steel spring 7 is secured and bentround. The free end of the steel spring 7 carries a bronze blade 6 whichserves for electric connection of the terminal 4 to the central pin ofthe lighter (not shown), this pin being electrically connected through arivet 5 in the form of an eyelet with through hole to a fusible washer 3of an electrically conductive lead alloy and a brass washer 2 forelectric connection of the device.

The bronze blade 6 extends in a plane perpendicularly to the plane ofthe steel spring 7 and has a semicircular recess at its free end whichfacilitates the insertion of the bronze blade 6 between the fusiblewasher 3 and the brass washer 2 and ensures its close engagement on theshaft of the rivet 5.

Thus the rivet 5 connects in the manner of a conventional riveting thesupporting receptacle 1, the fusible washer 3 and the brass washer 2 soas to form a single block thereof.

The alloy of the fusible washer 3 is so chosen that the washer will meltat a given temperature determined by the temperature of fusion of themetal alloy employed.

To facilitate the winding up of the steel spring 7, which carries theblade 6 projecting therefrom, the lower peripheral portion of thesupporting receptacle 1 is provided with a semicircular outer surface.

The invention may be embodied in other specific forms without departingfrom the spirit or essential characteristics thereof. The presentembodiments are therefore to be considered in all respects asillustrative and not restrictive.

lclaim:

I. An electric fuse for electric lighters in motor vehicles, comprisinga receptacle of insulating material for said electric lighter, anelectrically conductive terminal projecting from said receptacle, aresilient member connected at one end to said terminal and carrying atits opposite end a contact blade; said resilient member having a firstoperative and a second inoperative position, and electrically conductivetemperature responsive means insulatingly supported by said receptaclewith respect to said terminal for maintaining said resilient member insaid first position thereof at temperatures below a predeterminedtemperature and adapted to release said resilient member at temperaturesabove said predetermined temperature, and electrically conductive meansfor assembling as a unit said receptacle, said temperature responsivemeans and said resilient member in said first position thereof, saidlast-named means being adapted to engage a center projecting pin of acigarette lighter.

2. A fuse according to claim 1, wherein said receptacle is formed withan opening, said temperature responsive means comprising an electricallyconductive fusible washer having a face in substantial engagement withsaid receptacle and with the opening in said washer in alignment withsaid opening in said receptacle, and an electrically conductive endwasher on the opposite face of the fusible washer with its opening inalignment with the openings in said receptacle and in said fusiblewasher, said assembly means comprising a rivet extending through allsaid openings for holding together said receptacle, said fusible washerand said end washer.

3. A fuse according to claim 1, wherein said receptacle defines over atleast a portion of its periphery a curved surface adapted to guide saidresilient member into said first position thereof.

4. A fuse according to claim 2, wherein said resilient member comprisesa steel spring and said contact blade at said opposite end of saidmember comprises a bronze blade located in said first position of saidresilient member between said fusible washer and said end washer.

5. A fuse according to claim 4, wherein the bronze blade carried by thefree end of the steel spring extends in a plane 3,641,469 3substantially perpendicularly to said steel spring and has asemicircular recess at its free end to facilitate the insertion of thebronze blade between said fusible washer and said end washer to ensureengagement of the bronze blade with the shaft of said rivet. 5

1. An electric fuse for electric lighters in motor vehicles, comprisinga receptacle of insulating material for said electric lighter, anelectrically conductive terminal projecting from said receptacle, aresilient member connected at one end to said terminal and carrying atits opposite end a contact blade, said resilient member having a firstoperative and a second inoperative position, and electrically conductivetemperature responsive means insulatingly supported by said receptaclewith respect to said terminal for maintaining said resilient member insaid first position thereof at temperatures below a predeterminedtemperature and adapted to release said resilient member at temperaturesabove said predetermined temperature, and electrically conductive meansfor assembling as a unit said receptacle, said temperature responsivemeans and said resilient member in said first position thereof, saidlast-named means being adapted to engage a center projecting pin of acigarette lighter.
 2. A fuse according to claim 1, wherein saidreceptacle is formed with an opening, said temperature responsive meanscomprising an electrically conductive fusible washer having a face insubstantial engagement with said receptacle and with the opening in saidWasher in alignment with said opening in said receptacle, and anelectrically conductive end washer on the opposite face of the fusiblewasher with its opening in alignment with the openings in saidreceptacle and in said fusible washer, said assembly means comprising arivet extending through all said openings for holding together saidreceptacle, said fusible washer and said end washer.
 3. A fuse accordingto claim 1, wherein said receptacle defines over at least a portion ofits periphery a curved surface adapted to guide said resilient memberinto said first position thereof.
 4. A fuse according to claim 2,wherein said resilient member comprises a steel spring and said contactblade at said opposite end of said member comprises a bronze bladelocated in said first position of said resilient member between saidfusible washer and said end washer.
 5. A fuse according to claim 4,wherein the bronze blade carried by the free end of the steel springextends in a plane substantially perpendicularly to said steel springand has a semicircular recess at its free end to facilitate theinsertion of the bronze blade between said fusible washer and said endwasher to ensure engagement of the bronze blade with the shaft of saidrivet.